1. Field of the Invention
The present invention relates to a digital copying system and an image reading apparatus, and more particularly to a digital copying system which reads an image of a document while feeding the document with an automatic document feeder, carries out digital processing toward the image data and reproduces the image on a sheet.
2. Description of Related Art
In the art of electrophotographic copying system, it is generally known as a document-feeding image reading method to read an image of a document with a scanner which is set at an image reading position while feeding the document over the image reading position. In such a copying system adopting the document-feeding image reading method, the speed of feeding a document is varied in accordance with the copying magnification so as to achieve the registered magnification in the sub scanning direction. The magnification in the main scanning direction is varied by varying the movement of the optical system of the scanner.
In the document-feeding image reading method, the speed of feeding a document is gained more to achieve a smaller copying magnification, and in such a case, a large load is applied to a document from the transport rollers. Especially when a thin paper document such as a slip, a duplicate or the like is fed, there is fear that the document may be damaged.